KIT and gastrointestinal stromal tumor: And when GIST contains the PDGFRA mutation at exon 18, imatinib or other permitted TKIs will not work, while Avapritinib (BLU-285), one type I inhibitor of KIT and PDGFRA activation loop mutants, could be effective at most times and is now undergoing regulatory assessment as the fourth-line treatment for GIST in United States (Cassier et al., 2012; Rose, 2017; Dhillon, 2020).